Safety Aspects of Thermal Processing

Abstract

The aim of this text is to consider some of the engineering aspects of the thermal processing of packaged foods. These include the establishment of a thermal process through mathematical and experimental techniques, and the delivery of the thermal process, involving the correct operation and control of the process equipment. Many aspects of the complete process outlined in Fig. 1.1 have not been dealt with, in particular the food preparation operations, filling and seaming or sealing, can-handling procedures, and hygienic aspects of equipment design and operation. However, an attempt has been made to cover the main aspects of the thermal process and to review developments. In conclusion, it is necessary to consider some of the procedures used in what is today referred to as “good manufacturing practice” (GMP) in terms of legislation and processing guidelines. The aim of thermal processing of packaged foods is to assure that the food is free of microorganisms that can produce foodborne illness. In the case of canned food, the target microorganism is Clostridium botulinum, which produces a toxin responsible for serious illness in humans, called botulism. This toxin can affect the nervous system, causing paralysis and sometimes death. At the industrial level and because of legislation and code practices, foodborne botulism is uncommon and is a more complex trouble at the home canning level due to leakage of thermal processing. However, in the past, in the early stages of the canning industry and for close to half a century, the rapid spread of canned foods and evidence that they were causing illness led to recognition of the need to establish a means of assuring the safety of food products. For example, in 1918 in the USA, the first botulism commission was created. In 1922, it published its findings on the extent of botulism from commercially canned food. In 1922, Esty and Meyer determined the heat resistance of clostridium botulinum spores, establishing the basis of a microbiologically safe process for canned food. The recommendations proposed in this work for low-acid canned food were accepted by the US canning industry and later worldwide (Baird-Parker 1995).